Sigma term and strangeness content of octet baryons

TL;DR

This study uses lattice QCD and chiral perturbation theory to accurately determine the sigma terms and strangeness content of octet baryons, providing key insights into their quark structure.

Contribution

It combines lattice QCD data with chiral perturbation theory to improve the precision of baryon sigma terms and strangeness content estimates.

Findings

Nucleon sigma term 9(4)(+18/-7) MeV

Strangeness content y_N = 0.20(7)(+13/-17)

Alternative estimate y_N = 0.276(77)(+90/-62)

Abstract

By using lattice QCD computations we determine the sigma terms and strangeness content of all octet baryons by means of an application of the Hellmann-Feynman theorem. In addition to polynomial and rational expressions for the quark mass dependence of octet members, we use SU(3) covariant baryon chiral perturbation theory to perform the extrapolation to the physical up and down quark masses. Our N_f=2+1 lattice ensembles include pion masses down to about 190 MeV in large volumes (M_\pi L > 4), and three values of the lattice spacing. Our main results are the nucleon sigma term \sigma_{\pi N} = 39(4)(^{+18}_{-7}) and the strangeness content y_{N} = 0.20(7)(^{+13}_{-17}). Under the assumption of validity of covariant baryon \chi PT in our range of masses one finds y_{N} = 0.276(77)(^{+90}_{-62}).